Chair base



FIG. 1 is a perspective view of a chair base, showing our new design,the broken lines are for illustrative purposes only;

FIG. 2 is a right side elevational view of the chair base;

FIG. 3 is a top plan view of the chair base;

FIG. 4 is a bottom plan view of the chair base;

FIG. 5 is a left side elevational view of the chair base;

FIG. 6 is a front elevational view of the chair base; and,

FIG. 7 is a rear elevational view of the chair base.

The ornamental design for a chair base, as shown and described.